Bite Point

New Decay Preventing Strategy- Pro-t-action

Ever notice how some football tackles involve lots of defensive players just overwhelming the guy with the ball?  I've always found these to be one of the more interesting parts of the game.  There's usually nothing malicious about it- they're all just caught up in the moment, and they just keep glomming onto the ball carrier:

 

Well, BASF corporation is developing a new tooth decay preventive strategy that, on a microscopic level, looks an awful lot like a mass football tackle.  Or a rugby scrum, if you're from that side of The Pond.

As I reviewed back in 4/4//2009 in "The Resurgece of Dental Caries", there is one particular germ, Strep mutans, which lives in our mouths and eats some of the sugar that we eat and, as it does so, kicks out a tremendous amount of acid as a byproduct.  This acid can then decay our teeth if we are exposed to it too frequently. 

(See our "Caries Clock" @ http://www.smilephiladelphian.com/Clock/Caries.html )

For years dental researchers have tried to thwart the destructive plans of this single-mindedly nasty germ.  One approach from a few years back was to genetically engineer a strain that wouldn't produce so much acid, and then innoculate patient's mouths with this less damaging version of the Strep.  When that was being tried, my first question was, "How are they going to ensure that the less virulent strain out-competes the wild strain, and takes over in the patient's mouth?"  There are also the vast concerns about introducing genetically altered strains of bacteria into the world when we are really not yet fully able to predict the consequences of such manipulations.

BASF's approach, named pro-t-action, seems to take advantage of the more natural antagonisms between different bacteria.  Just like the Philadelphia Eagles and the Dallas Cowboys have a famous sports rivalry, germs compete against each other too. But instead of title wins, they are after resources in their environment.  Over thousands of years (and with generation times of as little as 20 minutes) they have developed offensive and defensive strategies that would make any football coach green with envy.

It turns out that a germ called Lactobacillus paracasei has developed a protein (probably back when our ancestors were trying to figure out how to walk on two feet, not four) that has the ability to:

-Target Strep mutans,

-Bind to them, and then,

-Clump them together, just like football's mass tackle or rugby's scrum:

A lot more germs clump together than there are players in the entire NFL, however, and once they do this, the normal actions of chewing and swallowing simply flush the clusters of them out of the mouth.  Other germs besides Strep mutans are not affected, since these antagonisms are very specific.  Also, not all of the Strep mutans would be washed out of the mouth, but most of them would be, and this may prove to be sufficient to stop the process of tooth decay in the human mouth. 

Unless you drink too much Gatorade- any system can be overwhelmed...

BASF has details (dry corporate ones, but details nonetheless) here:

http://www2.basf.us/corporate/news_2009/news_release_2009_00080.htm

We'll keep you posted as this concept is developed further.

Minimizing Post-Extraction Pain

Yesterday I had to extract a vertically fractured tooth for a long-time patient and friend.  The remarkable thing about this event is that it is the third unrestored tooth that he has fractured vertically.  That means these teeth had no fillings in them of any kind.  It is extremely common of course to fracture filled teeth, and sometimes the breaks travel vertically and split the tooth in half, a situation that we cannot repair.  But in my entire time in practice I've seen less than a dozen teeth break vertically when there were no fillings there to weaken them ahead of time.  And three were owned by this fine gentleman...  (Strong muscles and grinding patterns are part of the reason why.)

I can still recall all three incidents.  In the first, years ago, I had worked until 7:00 PM and arrived home in a state of ravenous hunger.  I had just stuck my fork into a beautiful and aromatic plate of pan-seared vegetables and meat when the call came- sudden agony, just intractable pain.  Back to the office in a flash; I mean, relieving our fellow humans from physical suffering scores fairly high on the Index Of Noble Acts, does it not?  The whole thing reminded me of the Adam's Ribs episode in the third season of M*A*S*H, in which Hawkeye goes to inordinate lengths to have barbecued spareribs delivered all the way from Chicago to Korea, only to have to rush to the O.R. just as the plate is put in front of him:  http://en.wikipedia.org/wiki/Adam%E2%80%99s_Ribs

The second time was in August a few years back.  Motoring along West River Drive in Philly towards the office, I saw the sun reflecting a gorgeous red glow on a railroad bridge and snapped a pic that remains the background on the computers in Room 4 to this day; patients comment on it all the time.  Such a rare pic- the sun only achieves the required angle for a few days each year, and for a few minutes on each of those days:

This third fracture episode led to a very difficult extraction.  Teeth which fracture often have a network of cracks in them.  As we apply pressure to elevate them out, their brittle nature leads to pieces cracking away.  Add in very strong, dense bone to the clinical scenario and we have a real challenge.  I used modern instruments called periotomes to free up the root, but still had to resort to some minor removal of supporting bone in order to complete the extraction.  This is the part of the process that always used to lead to severe post-operative pain.  Tooth extraction sites heal by first filling with a blood clot.  The body sends in immune cells and inflammatory chemical messengers; later on blood vessels migrate in and eventually bone forms in the socket- but it's a lot less bone than we'd like.  And the more trauma during the extraction, the more post-op pain.

For some years now we've recommended that bone grafting materials be placed in the extraction site in most cases.  These are minerals- specifically hydroxyapatite, the main mineral in our bones- from various sources which act as a scaffolding to help the body heal more fully.  We gain both better bone quality, and more bone quantity, or volume.  This result vastly improves the outcome for tooth replacement with a dental implant.  It also improves the outcome for a conventional bridge, if that is chosen for the means of tooth replacement, because the bone doesn't shrink as much.  (If the bone shrinks back a lot, it leaves us with the artificial tooth being all long and Bugs-Bunny-esque.)

Bone grafts also drastically reduce post-operative pain levels.

This extraction yesterday was so difficult...  And yet I called my patient last night and, voila, he was doing very well with low levels of pain, taking reasonable doses of pain medication.  Why?

I had placed bone graft materials, sutured, and covered the socket with Histacryl, a medical-grade cyanoacrylate which provides a covering and biological seal over the site for the first week or so.  Based on the biology of the situation, here's what I believe happens:

-In open, untreated extraction sites, high levels of inflammatory cells and chemical mediators migrate in, since the body views this as a major wound that has to "fill in" from around its edges.  The body must protect itself from infection too, and the gaping void left after removing something as large as a tooth poses a significant infection risk.  The immune system says, in effect, "Time to send in the troops!"

-In grafted, covered sites, I believe that the immune cells and the chemical messengers of inflammation migrate in in less quantity, and also that their relative ratios are different than in open sockets.  In other words, the inflammation and pain is greatly reduced, and the reason is that the body percieves this sort of wound as much less of a threat, and it heals more rapidly and predictably.  It's like the difference between sanding and preparing the walls of your house for new paint, and gutting your house and starting from sctatch. 

If your walls are OK to begin with, which would you rather do?

Note to the scientists out there, especially the ones in Gstaad that re-name things all the time (4/16/09 & 5/21/10): Yes, this is anectdotal evidence, although I have seen low post-op pain levels with bone grafts with very high consistency for about a decade now.  This observation does need to be studied further in an academic setting.

So in summary, bone grafts after tooth extractions help maintain bone quantity and quality, improve the prognosis for dental implant or bridge tooth replacement therapy, and dramatically reduce post-operative pain levels.

I'm Proud of Dentistry's Long History of Diversity

I shall reprint, from our website, the moving and astonishing story of Dr. Robert Tanner Freeman, the first African-American to ever graduate from an American dental school.

It was in 1869, by the way.  That's truly an "eight" in the second digit, not a typo. 

First, a few thoughts. 

I teach part-time at the dental residency at Albert Einstein Medical Center here in Philly.  The residents are graduating soon and I got to thinking about how diverse my profession is and has always been.  And yet this diversity is that special kind- the kind that is not imposed upon us by the force of law, or by protestors angrily waving signs in the streets, or by the victims of raw intolerance writing plaintive letters asking that their talents be recognized in spite of some attribute like their religious beliefs or the amount of melanin in their skin.

Diversity not forced.  So different from:

 

-Which had magnificent results, yet this philosophy of diversity that I speak of in dentistry is singular because it comes from within the profession, from the hearts and minds of the members, not because of external pressures.

When I think of my many friends and colleagues who are dentists and specialists, the number of regions where either they or their immediate ancestors originate from is truly astonishing.  I have dentist friends who are originally from India, Iran, England, Israel, Sweden, Hungary, Vietnam, Tanzania, Sudan, China, Saudi Arabia, Dominican Republic, Egypt, Thailand, Colombia, Germany, South Africa, Iraq, Italy, Korea, Ireland, Turkey, Japan, Ghana...  Even New Jersey, for heaven's sakes!  Not to mention their various ethnic or religious backgrounds, or other ways of looking at diversity.

When he was living, the remarkable dentist Dr. Robert Burkhardt was historian of the Academy of Stomatology of Philadelphia, a continuing education society founded in 1894.  (No, I was not a founding member!)  He used to pull out minutes from meetings long ago and briefly read from them.  Seems that in the late 1920's a "person of color" applied for membership in this select group.  There was considerable discussion, and it took awhile to come to a decision, but, extraordinary for those days, the answer was yes.  Can you magine how many private groups and clubs in the 1920's were exclusionary?  Almost all of them.

Here then is Dr. Freeman's story. If I had a time machine with ten trips at my disposal, meeting him would be one of them.

 

Robert Tanner Freeman was born in Washington DC in 1846. He was the son of slaves who had bought their freedom in the 19th century. Historical records are unclear but they probably adopted the surname "Freeman" in response to their transition.

In these days many dentists learned their profession- really more properly "trade" at this time- as apprentices and laboratorians. The first University based formal dental school was Harvard Dental School, founded in 1867.

Robert had a strong interest in the health professions, and he sought work as a dental assistant and clerk from Dr. Henry Bliss Noble, his white dentist who tutored Dr. Freeman and encouraged him to pursue his own career in dentistry. Dr. Noble hired Robert to work in his office which was in the 1500 block of Pennsylvania Avenue in Washington, DC. At this time it is estimated that there were a total of 120 African American dentists in the entire US, all having started via apprenticeship not through formal, college education.

Dr. Noble "was a reputable dentist whose humane acts of employment and encouragement of an African American were indeed remarkable, especially in the nation's capital where residents were sensitive to Confederate values and traditional interracial dogma," wrote dental historian Dr. Clifton O. Dummett in "Courage and Grace in Dentistry: The Noble, Freeman Connection," from the Journal of the Massachusetts Dental Society (1995).

Dr. Noble "encouraged him to think seriously about pursuing a dental career, pointing out that Freeman would be in a better position to help alleviate human suffering and serve the dental health needs of his fellow African Americans in this way."

Robert applied to and was rejected from two dental schools on racial grounds.

Then, Dr. Noble set about the process of working his colleagues.

He was well acquainted with Dr. Nathan C. Keep, Harvard Dental School's first Dean, and other members of the Board of Trustees. Dr. Noble strongly lobbied these men to accept his African-American employee and friend into the first class of their new school. At first there was resistance, and they too considered rejecting Robert's application. As they met, however, the conversation must have taken an unexpected course, as it often does in a new, creative group of people. These people were, after all, taking what was a trade and molding it into an integral part of the medical profession. On Dr. Keep's recommendation, Harvard decided the school would "know no distinction of nativity or color in admitting students." They also stated that they wished to establish a tradition of inclusion not exclusion as they began their enterprise. Dr. Freeman thus became the first African-American graduate of a US dental school in history.

After graduating from Harvard in 1869, Dr. Freeman returned to Washington, D.C., and practiced in the same building as his mentor, Dr. Noble. Unfortunately, his death came only four years after dental school. He contracted one of the water-borne diseases so common at that time, cholera I believe. Every indication is that he served his community in an exemplary way and gave vital assistance to an African-American community in a time of tremendous cultural and political change. Recall that the American Civil War had only ended 4 years before his graduation.

His career also began a distinguished legacy for his family. Dr. Freeman's grandson, Robert C. Weaver, Ph.D., became the country's first African-American presidential cabinet member, serving as Lyndon B. Johnson's Secretary of Housing and Urban Development.

None of this success would have happened without a small group listening to a few of its influential members who stood up for something that must have been exceedingly unpopular at the time. I also find it interesting and inspiring that the decisions of a relatively small circle of people in the 1860's could reverberate down through time into the 1960's and influence choice at the presidential cabinet level. Dr. Weaver would not have been able to reach his own success without building on that of his grandfather.

Orthodontic Relapse and Invisalign

Even teeth that come in perfectly straight or are set up that way by an orthodontist are not going to stay that way.  No, there are two major forces on our teeth that conspire to move them around, often in predictable ways.  Let's examine them.

First, teeth want to move towards each other.  Such sociable little creatures they are.  Let's examine how they travel. 

There are two directions going on here.  Our teeth try to erupt towards the ones in the opposite arch.  Lowers upwards, uppers downwards.  They also have a built-in march to the front.  This is  because our distant ancestors used to have a much more harsh diet than we do now.  They'd basically wear their back teeth down flat by the time they were in their early 20's.  My friend Dr. Janet Monge PhD is a professor of physical anthropology at Penn.  She's also imho the most brilliant and entertaining academic in Philly.  I once engaged her to give a talk to a dental group which she titled "The Evolution of the Human Dentition: From Nuts to Soup."  What she explained is that our predecessors didn't cook foods so much as we do today, and they also ground up many grains using stones.  All that stone grit got in there and over time wore away their tooth enamel. 

This grit also wore the teeth in between, where they touch.  So to avoid gaps, they migrated, through bone changes, towards each other. 

So we have all these teeth wearing away and erupting towards each other, and they also marched towards the front.

Here's how their teeth used to look:

Since most of us don't eat rocks these days, we don't suffer this degree of wear, or attrition.  We do still have those forces on our teeth though and they still try to move, especially forward.  Crowding results:

 
Once they slide past each other, it gets worse- fast.

Another type of tooth movement that plagues us is that the powerful muscles that close the jaws apply more pressure inward, over time, than the tongue does in an outward direction.  This happens in most, but not all, people.  The disequilibrium between these forces, well, forces our back teeth inwards.

As an aside, orthodontists sometimes bond in semi-permanent retainer wires in the back of the six lower front teeth.  Since the lower teeth generally fit inside the upper teeth, the lowers drive the upper crowding or flaring, so to a point keeping those lower front six straight works.  However- the back teeth are still subject to the muscle forces that push them inward.  So they move anyway.  The bonded retainer also impedes flossing.  Overall, I'm not so favorable towards these bonded retainers because they really only solve half the problem, and at the expense of effective oral hygiene.

Invialign (http://www.invisalign.com/Pages/Home.aspx) can do some things exceptionally well.  Other orthodontic challenges are best handled by conventional braces.  Generally speaking, dealing with the relapse caused by the forces described above is one of the areas where Invisalign excels.  Have a look at one of my favorite uncrowding cases, in just one view of the pre-treatment simulation.  Watch just the front teeth first, as you see them uncrowd from their March To The Front, then watch the back ones as they unravel from the Tongue-n-Cheek Tango.  Both sets of forces beautifully dealt with!

Download L2

Invisalign retainers, called Vivera, really rock out by the way.  They encase the entire arch of teeth in precision fitting plastic and can be renewed from reproducible digital information at any time.  As long as patients don't let their teeth get too far out of line, Vivera will keep them in whatever position they were in when the impression was taken.  And they're only worn at night.

Watch your cholesterol.  Change your oil.  Wear your retainers.  Hey, no one said living responsibly was easy.